Heat gain and contribution to heating from supplemental lighting in greenhouse

Supplemental lighting sources in greenhouses are accompanied by generation of considerable amounts of heat. However, the engineering methods regarding this contribution to greenhouse heating are rarely recognized. This study was conducted to evaluate the experimental and theoretical heat gains from supplemental lighting and their contributions to greenhouse heating. The experimental greenhouse had glass covers and 100 m2 floor area, and 21 high pressure sodium lamps of 250 W were used as the light source. The greenhouse operated with thermal screens at night in winter and spring. The heat gain from lighting for 5 h a day was evaluated to be maximum 91.3 MJ, and the effective contributions of lighting to heating were evaluated to be between 12.8% and 72.2%.